Applicants claim, under 35 U.S.C. xc2xa7 119, the benefit of priority of the filing date of Apr. 16, 1999 of a German patent application, copy attached, Ser. No. 199, 18 654,5, filed on the aforementioned date, the entire contents of which is incorporated herein by reference.
1. Field of the Invention
The invention relates to a measuring system for determining the position of two machine components that are movable in relation to each other, having a securing device for transport and mounting.
2. Discussion of Related Art
A measuring system of the type mentioned at the outset and having a securing device is known from DE 30 20 003 C2. Here, a measuring system includes a longitudinally extending measuring graduation, a support body supporting the measuring graduation, a scanning device scanning the measuring graduation, which is guided at a defined distance from the measuring graduation, and a mounting base connected with the scanning device for fastening the scanning device on one of the components which are movable with respect to each other. The two components, which are movable with respect to each other, can be the carriage and the associated base of a machine tool in particular. In this case, the support body with the measuring graduation on the one hand, and the mounting base with the scanning device on the other, are respectively fastened on one of these components. The securing device itself has two base bodies, which can be displaced along a guide slit in the support body. A resilient tongue is arranged on each base body, by means of which the securing device can be clamped to the support body in order to maintain the mounting base on the support body in a defined prescribed position during the transport and mounting of the measuring system
The known securing device has the disadvantage that it merely permits a fixing in place, which involves play, of the mounting base, and therefore also of the scanning device, on the support body since, in order to be able to remove the securing device again from the support body at the termination of mounting the measuring system on a machine tool, the resilient tongue of the securing device must be designed to be sufficiently elastic.
A mechanism for fastening a measuring system containing a magnetic scale on a machine tool is known from DE 35 27 652 A1, which includes a securing device, by means of which the support bodies of the magnetic scale and the associated scanning device are aligned with each other during mounting. This securing device has the disadvantage that it is only insufficiently guided on the support body.
A measuring system for monitoring relative displacements is known from DE 39 17 717 C2, which is intended to determine the displacement of machine elements of a machine tool that can be moved in relation to each other. A locking device is employed during mounting of this measuring system on the machine tool, by means of which the scanning device of the measuring system can be maintained in a position in which it does not. interfere with the mounting operation. This locking device includes a plastically or elastically deformable material, so that it can be clipped to the support body. Because of its deformability, this locking device is therefore not suited to fix the position of the support body on the one hand, and of the scanning device on the other hand, in a manner which is free of play to a great extent.
The measuring system in accordance with EP 0 323 550 B1 has a securing device which is clamped in the support body by tilting. For clamping, the securing device is supported on the one hand on the support body and, on the other hand, has an element that is rigidly fastened on it and engages a groove of the support body. Because of this engagement it is difficult to remove the securing device from the measuring system.
It an object of the present invention to create a measuring system for determining the position of two components which are movable in relation to each other, having a securing device for the transport and mounting of the measuring system, wherein the support body as well as the scanning device of the measuring system can be fixed in place essentially without play in a defined relative position, and wherein the securing device can be removed in the easiest possible manner at the termination of mounting of the measuring system.
The securing device is used for fixing the scanning device of the measuring system in a defined position (prescribed position) on the support body of the measuring system during the transport and mounting of the latter.
The securing device in accordance with the present invention has the advantage of making possible a very stable, essentially rigid fixation in place of the mounting base of the scanning device on the support body, in that the guide element of the securing device is fastened with clamping forces of an appropriate strength on the support body. The securing device can also be simply removed from the support body at the termination of mounting, in that the connection between the base body and the guide element of the securing device is released. The base body can then be simply removed. The guide element either remains in the associated guide track of the support body, or is removed from it. In the latter case the guide element must be designed in such a way that its interlocking connection with the guide track of the guide body can be released after the base body has been removed.
Accordingly, the present invention is able to position a scanning device at a defined position of the support body of a measuring graduation, in that the mounting base of the scanning device is slid, together with the securing device, along a guide track of the support body into a predetermined position. There, the mounting base, and therefore also the scanning device, are then fixed in place by providing a clamped connection between the securing device and the support body. In this case, the guide element of the securing device is preferably rigidly embodied in such a way that it can be clamped in place, free of play, on the support body by clamping forces acting transversely to the measuring direction.
Because of the possibility of being able to hold the mounting base free of play in a defined position on the support body by the securing device in accordance with the present invention, during mounting of the measuring system it is now possible, because of the preset position of the mounting base on the support body, to align the two components of the machine tool which are movable in relation to each other. These two components need not necessarily be machine parts, such as the base and the carriage of a machine tool; instead it is also conceivable that additional added-on elements, which support the measuring system and which are aligned with each other in the course of mounting the measuring system, are provided on these machine parts. In this case, the base and the carriage of the machine tool can already be aligned with each other prior to mounting the measuring system.
The connector elements, through which the base body and the guide element of the securing device are connected with each other, are preferably used for generating the required clamping forces. This can be a screw connection, for example.
The guide track of the support body can be a guide groove with an undercut, so that the guide element can be arranged interlocked and longitudinally displaceable in the guide groove.
In a preferred embodiment of the present invention, the securing device is constituted by two separate base bodies, which are arranged, spaced apart in the measuring direction, on respectively one of the front faces of the mounting base. It is possible here to assign each of the two base bodies its own guide element; on the other hand, however, the two base bodies can also be rigidly connected with each other via a common guide element. In the first case, a rigid arrangement of the two base bodies with respect to each other can be achieved by an additional bracket connecting the two base bodies with each other. In the second mentioned case, a dependable support of the mounting base on both sides in its prescribed position is made possible with only three components. Here, the guide element additionally takes on the function of the securing bracket.
An arrangement of the securing device on the support body, which is essentially free of play, can in particular be achieved if not only its guide element is clamped in place on a protrusion of the support body extending along the guide track, but in that the base body of the securing device is additionally supported on the support body outside of the guide track. In this case, the base body can operate in a longitudinally displaceable way together with the support body, for example, by a groove and tongue connection.
In a preferred embodiment of the present invention, an aligning device is provided for aligning the mounting base in relation to the support body. For example, the aligning device can include a tongue arranged on the security device so that the distance between the mounting base and the support body transversely in respect to the measuring device is fixed.
Moreover, the aligning device can include connecting elements, which provide an interlocking connection between the securing device and the mounting base. For example, this can be a connection, wherein a peg of the mounting base or of the securing device, respectively, projects into a recess of the other component which is assigned to it, wherein the peg and/or the recess preferably have bevels or chamfers for compensating manufacturing tolerances. But a force-locking or frictional connection between the securing device and the mounting base is also possible.
Furthermore, in order to be able to compensate for tolerances that must be taken into consideration when fastening the measuring system on a machine tool, the play of the interlocking connection between the securing device and the mounting base can preferably be varied. For this purpose, it is possible to provide a number of different connecting elements on the securing device and/or the mounting base, respectively, one part of which is selected for making the interlocking connection. For example, different connecting elements can be respectively arranged on both front faces of the base body of the securing device, so that the play in the connection between the securing device and the mounting base can be varied in that the base body of the securing device is fastened either by the one or the other front face on the mounting base.
Different connection elements in particular can be employed for varying the play of the connection between the securing device and the mounting base that, although their exterior shape agrees, differ in size.
The play between the securing device and the mounting can also be varied, in particular when using pegs provided with bevels or chamfers for connecting the securing device and the mounting base, in that the distance between the base body of the securing device and the mounting base can be varied. This can take place, for example, in that the base body and guide element of the securing device can be connected in different positions in relation to each other.
Further advantages of the invention will become apparent in the course of the following description of an exemplary embodiment, making reference to the drawings.